import sys, math
from collections import defaultdict, deque, Counter
from bisect import bisect_left, bisect_right
from itertools import combinations, permutations, product
from heapq import heappush, heappop
from functools import lru_cache
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mat = lambda x, y, v: [[v]*y for _ in range(x)]
ten = lambda x, y, z, v: [mat(y, z, v) for _ in range(x)]
mod = 1000000007
sys.setrecursionlimit(1000000)

K = ri()

if K % 2 == 0:
	print(-1)
	exit()
r = 0
for i in range(10000000):
	r = (r*10+7) % K
	if r == 0:
		print(i+1)
		exit()
print(-1)
 import sys, math sys math from collections import defaultdict, deque, Counter from bisect import bisect_left, bisect_right from itertools import combinations, permutations, product from heapq import heappush, heappop from functools import lru_cache input = sys.stdin.readline input sys.stdin.readline sys.stdin sys stdin readline rs = lambda: input().strip() rs lambda: input().strip() input().strip() ().strip () input strip ri = lambda: int(input()) ri lambda: int(input()) int(input()) int input() input rl = lambda: list(map(int, input().split())) rl lambda: list(map(int, input().split())) list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split [v]*y for _ in range(x) for _ in range(x) _ range(x) range x for _ in range(x) [v]*y [v] v y mat = lambda x, y, v: [[v]*y for _ in range(x)] mat lambda x, y, v: [[v]*y for _ in range(x)] [[v]*y for _ in range(x)] x y v mat(y, z, v) for _ in range(x) for _ in range(x) _ range(x) range x for _ in range(x) mat(y, z, v) mat y z v ten = lambda x, y, z, v: [mat(y, z, v) for _ in range(x)] ten lambda x, y, z, v: [mat(y, z, v) for _ in range(x)] [mat(y, z, v) for _ in range(x)] x y z v mod = 1000000007 mod 1000000007 sys.setrecursionlimit(1000000) sys.setrecursionlimit sys setrecursionlimit 1000000 K = ri() K ri() ri if K % 2 == 0:
	print(-1)
	exit() K % 2 == 0 K % 2 K 2 0 print(-1) print -1 exit() exit r = 0 r 0 for i in range(10000000):
	r = (r*10+7) % K
	if r == 0:
		print(i+1)
		exit() i range(10000000) range 10000000 r = (r*10+7) % K r (r*10+7) % K r*10+7 r*10 r 10 7 K if r == 0:
		print(i+1)
		exit() r == 0 r 0 print(i+1) print i+1 i 1 exit() exit print(-1) print -1 r = (r*10+7) % K (r*10+7) % K r rs = lambda: input().strip() lambda: input().strip() rs input = sys.stdin.readline sys.stdin.readline input rl = lambda: list(map(int, input().split())) lambda: list(map(int, input().split())) rl mat = lambda x, y, v: [[v]*y for _ in range(x)] lambda x, y, v: [[v]*y for _ in range(x)] mat ten = lambda x, y, z, v: [mat(y, z, v) for _ in range(x)] lambda x, y, z, v: [mat(y, z, v) for _ in range(x)] ten ri = lambda: int(input()) lambda: int(input()) ri mod = 1000000007 1000000007 mod r = 0 0 r K = ri() ri() K
import sys, math
from collections import defaultdict, deque, Counter
from bisect import bisect_left, bisect_right
from itertools import combinations, permutations, product
from heapq import heappush, heappop
from functools import lru_cache
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mat = lambda x, y, v: [[v]*y for _ in range(x)]
ten = lambda x, y, z, v: [mat(y, z, v) for _ in range(x)]
mod = 1000000007
sys.setrecursionlimit(1000000)

K = ri()

if K % 2 == 0:
	print(-1)
	exit()
r = 0
for i in range(10000000):
	r = (r*10+7) % K
	if r == 0:
		print(i+1)
		exit()
print(-1)

